In Section  we discuss the boundary layer phenomenon arising in the
vicinity of the perforation. In particular, we examine several
solutions of the Laplace equation in the unbounded strip \(\Pi \)  with the only
hole \(\overline{\omega }\) , and we introduce the integral characteristics
\(m_1(\Xi )\) , \(m_2(\Xi )\)  and \(m_3(\Xi )\)  for the Neumann problem in the
domain
\(\Xi =\Pi \setminus {\overline{\omega }}\) 
(see Figure REF  and (REF )) with the periodicity conditions on the lateral sides, cf. the
traditional harmonic polarization and virtual mass tensors in the
exterior domain \({\mathbb {R}}^2\setminus \overline{\omega }\)  in [1]}.
